I am considering buying a 2002 x-type 3.0 with 30k miles. It does have problems, the transmission slips and thus motor races. It has codes P734 and P735. What are the range of problems that could be causing this, and the cost range to fix it? Or should I just avoid the car?

 

Code P0734 When the code P0734 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is seeing a greater than a specified RPM difference between the rotational speed of the Input RPM Sensor and the Transmission Output RPM Sensor when the vehicle is in 4th gear.

SOLVED: I have a gearbox error showing on the dash and i - Fixya

https://www.jaguarforum.com/showthread.php?t=38107

Code P0735 When the code P0735 is set in the Powertrain Computer, it means that the Powertrain Computer or PCM is seeing a greater than a specified RPM difference between the rotational speed of the Input RPM Sensor and the Transmission Output RPM Sensor when the vehicle is in 5th gear.

https://www.justanswer.com/jaguar/6a...slips-5th.html

Causes =

The transmission fluid is low or dirty.
The transmission main control is suffering from internal blockage.
Shift solenoids.
Transmission hydraulic control circuit.
Mechanical problems inside the transmission.

 

Transmission repair is so expensive, you can buy repair manual, learn how to repair it and do it yourself (if you consider yourself a smart guy). It can need very simple repair but you'll get ripped off.
Here is example: seller of my Jag said "possibly bad ECM", this is what his mechanic told him. It turned out to be 3 bad ignition coils and O2 sensor. I got everything from junk yard dirt cheap. I actually got new ignition coils, because they have different shape and one of 3 Jags there had all new coils. Of course I got used O2 sensor, I am not paying $90 or so!
there were some more problems, easy ones: bad water pump, and windshield pump